[llvm] AMDGPU: Mark v_mov_b64_pseudo as a VOP1 instruction (PR #128677)

[Jay Foad via llvm-commits]

https://github.com/jayfoad approved this pull request.

Seems reasonable. Which part of the remat implementation cares about the VOP1 flag?

https://github.com/llvm/llvm-project/pull/128677